Chaeles e



(No Model.) C. E. SORIBNER.

TEST CIRCUIT FOR MULTIPLE SWITCH BOARD SYSTEMS. No. 356,425. PatentedJan. 18,, 1887'.

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IlsiiTnn STATES PATENT Orricn.

CHARLES E. SCRIBNER, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE \VESTERNELECTRIC COMPANY, OF SAME PLACE.

TEST -CIRCUIT FOR MULTIPLE-SWITCH-BOARD SYSTEMS.

SPECIFICATION forming part of Letters Patent No, 356,425, dated January18, 188?.

Application filed November 6, 1886. Serial No. 218,193. (No model.)

To all whom it may concern.-

Be it known that I, CHARLES E. ScRIB vER, a citizen of the UnitedStates, residing at Chicago, in the count-y of Cook and State ofIllinois, have invented a certain new and useful Improvement inTest-Circuits for Multiple- SWitch-Board Systems of aTelephone-Exchange, (Case 112,) of which the following is a full, clear,concise, and exact description,

[0 reference being had to the accompanying drawing, forming a part ofthis specification.

My invention relates to test-circuits for mul tiple-switch-board systemsof a telephone-exchange, and relates more especially to the sys terndescribed and claimed in my Patent No.

305,021 of September 9, 1884.

The telephone-lines are connected each with a different switch upon eachof the switch- .boards, and each line passes through its indi- 2o vidualannunciator and a flexible cord and plug, and thence to ground at thecentral office. Telephone-lines thus including cords and plugs in theircircuits are shown in Letters Patent No. 306,414 of October 14, 1884.

Heretotore in systems in which cords and plugs are included in thecircuits of the different lines, so that one line may be connecteddirectly to the spring-jack of another line by inserting the plug, notest has been provided whereby the line of the subscriber whose plug isinserted in the spring-jack of another line may be tested to determinewhether or not that line is busy. The line of the calling subscriber isconnected with the spring-jack of the subscriber called by inserting theplug of the calling subscriber in a spring-jack of the calledsubscribers line. The plug thus'inserted will furnish the necessarycross or connection with the test-wire of the called subscriber, but, asabove stated, there will be no means of testing the line of the callingsubscriber, since no connection will be made with any of thespring-jacks of the said calling subscribers line.

The object of my invention is to provide a connection whichautomatically closes the testwire of the calling subscribers line toground when the line is put into use. I do this by placing in eachcircuit a listening-key, the plunger of which connects with thedifferent test-rings of the spring-jacks of that line, the

listening-key being so connected that when the line is in use theplunger becomes connected or crossed with the said telephone-linethrough the medium of the springs of the listeningkey. Thus all thetest-rings of the springjacks of the calling-line are connected with theline through the medium of the plunger. When a line is busy, by touchingthe plug of the operators telephone and battery to a testring of saidline at any board, circuit will be closed through the telephone, and theoperator will know by the click in the telephone that the line is busy.The act of throwing down the cam-lever of the listening-key forces 6down the plunger and disconnects the line I from ground, and the normalconnection between the plug and the operators telephone is broken, andthe line is connected through the head of the plunger to the cord andplug, and thence to the line into whose spring-jack the plug isinserted.

My invention is illustrated in the accompanying drawing, in which I haveshown see tions of two multiple switch-boards with two 7 telephone-linesand test-circuits connected therewith, the operators calling and testingapparatus being shown at each of the boards.

The circuit of telephone-lineamay be traced through its switches on thedifferent boards to its individual annunciator b, and thence to key aand spring (1 of the listening-key, said spring normally resting uponthe ground contact-point 6. Each telephone-line is thus normallyconnected to ground. .8

The test-wire of line a is connected with the test-ring of each of thedifferent switches of the line upon the different switch-boards. Thistest-Wire is connected also with the plungerg of the listening or loopkey, and it is through this connection that the cross between thetest-wire f and the telephone-line a is established when saidtelephone-line a is connected with another line for the purpose ofindicating that said line is busy.

It will be observed that a contact-point, h, is provided below the key0. WVhen a call is sent in over line a, shutter b is thrown down, andthe operator, by pressing down upon plug z, closes the key 0 uponcontact-point h, thus IOO bringing the operator s telephone into thecircuit of telephoneline a. The operator thus while holding down key 0finds out what connection is wanted. He thereupon takes up plugi to testthe line called for, and key 0 re sumes its normal position in contactwith spring 61 of the listening-key. In this position it will beobserved that when the plunger is raised and the springs of thelistening-key are resting upon their contact-points, respect ively, theoperators telephone will be included in the circuit of the cord andplug. This circuit may be traced from the plug through the cord to keyit, said key normally making contact with spring Zof the listening key.This spring is connected with contact-point m, and from this point thecircuit may be traced through the telephone to ground. The.plug beingthus connected with the operators telephone is applied to the test'ringof the switch of the line wanted in the usual manner to determinewhether the line is busy.

\Ve will suppose, now, that the linetests not busy. The operatorthereupon inserts the plug in the spring-jack of the line wanted,andthen forces down the plunger, so as to connect the two springs of theloop-key together through the medium of the plunger. The two lines arethus connected together for con versation, and the test-wires of the twolines are crossed with their respective lines. The test-wire ot' thecalled line is crossed at the springjack through the medium of a plug.The test-wire of the calling-lineis crossed with its line through themedium of the plunger 9 of the listening-key.

A test may thus be made at any of the boards to determine whetheranylinebe busy, whether that1inebeconnectedthroughthemediumofits terminal plugor through th e' medium of one of its spring-jacks. For convenience, Ihave provided at each board an extra plug, a, which the operator maycarry in his hand. The subscriber wanted may be notified of the call bydepressing key after the plug 1' has been inserted in the spring-jack ofthe called subscriber.

NVhen key is is depressed, the circuit from the generator 0 may betraced, as shown, to said key it, and thence through the cord to theplug, and when the plug is inserted in a springjack to the lineconnected with said springjack.

It will be observed that the flexible cord and plug are not normallyincluded in the circuit of the line when the line is not in use. When,however, the plug of a line is inserted in the spring-jack of anotherline, and the springs of the loop-key are connected together, the plugand cord are included in the circuit.

Having thus described myinvention, I claim as new and desire to secureby Letters Patent 1. The combination, with the test-wire connected withthe insulated frames or test-pieces of the different switches of atelephone-line, of a ground-connection and switching apparatus, wherebysaid test-wire may be connected to ground when said line is connected tothe switch of another line.

2. The combination, in atelephone-exchange switching apparatus, withatelephone'line c011- nected with switches distributed on differentboards and through an annunciator and listening or loop key to ground,of a test-wire for said line and a connection from said loopkey to thetest-wire, whereby a ground-connection is provided for said testwire.

3. A telephone-line connected with two or more multiple switch'boardsand through an annunciator and switching device to ground, incombination with a plug supported by said switching deviceandacontact-point connected with the operators telephone-outfit, whereby'on depressing'said plug the telephone-line is disconnected from itsnormal ground and connected with the operator's telephone, substantiallyas shown and described.

4. A telephone-line connected with two or more multiple switch-boardsand through an annunciator and loop-key to ground, in combination with aflexible cord and plug and a key, It, and a generator, whereby ondepressing said key the cord and plug are disconnected from thetelephone-line and connected with the generator, substantially as shownand described.

In witness whereof I hereunto subscribe my name this 1st day ofNovember, A. D. 1886.

CHARLES E. SORIBNER.

Witnesses:

GEORGE P. BARTON, CHAS. O. WooDwoR'rH.

